docs: document the plain output format and yaml/md aliases

[rajarshidattapy]

Description

Fixes #201

The Output Formats section of docs/cli-reference.mdx listed five formats — table, json, yaml, md, csv — but eight are supported (src/command-surface.ts:5):

export const OUTPUT_FORMATS = ['table', 'plain', 'json', 'yaml', 'yml', 'md', 'markdown', 'csv'] as const;

This adds -f plain to the example block and one sentence covering what plain does and the two aliases.

plain was the notable omission. It is dispatched at src/output.ts:50 and appears in both help strings — src/command-surface.ts:72 builds the -f help from OUTPUT_FORMATS.join(', '), and src/command-presentation.ts:91 spells out "table, plain, json, yaml, md, csv" — and skills/webcmd-usage/SKILL.md documents it for agents. The published reference was the only place it was missing, so it was invisible to anyone reading the docs rather than running --help.

Behaviour documented, taken from formatPlain (src/output.ts:123-146):

Claim	Source
prints key: value lines instead of a table	src/output.ts:137-144
prints the bare value for a single field named response, content, markdown, text, or value	src/output.ts:127-134
yml is an alias for yaml, markdown for md	src/output.ts:51-55

Related issue: Closes #201

One thing intentionally left undocumented

-f is not validated. OUTPUT_FORMATS is used only to build help text, never to check the supplied value, so an unrecognised format falls through the default: case in formatOutput (src/output.ts:56) and silently renders a table — -f jsonn produces table output with no error.

I left that out of the docs because it reads as a defect rather than intended behaviour, and writing it down would bless it. Happy to open a separate issue for it if that is useful. If -f gains validation later, the alias sentence added here stays correct and a rejection note becomes worth adding alongside it.

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🌐 New site adapter
• 📝 Documentation
• ♻️ Refactor
• 🔧 CI / build / tooling

Checklist

• I ran the checks relevant to this PR
• I updated tests or docs if needed
• I included output or screenshots when useful

Notes on the checklist:

• Docs-only change to one .mdx file; no code, tests, or generated artifacts are touched. Each claim was verified against src/ rather than by running the suite.
• No automated check covers this page's contents. src/docs-sync-review.ts lists docs/cli-reference.mdx as a watched path only, which is why the drift went unnoticed.

Adapter Notes

Not applicable — no adapter is added or modified in this PR.

• Updated generated or lean docs when command discoverability changed
• Used positional args for the command's primary subject unless a named flag is clearly better
• Normalized expected adapter failures to CliError subclasses instead of raw Error

Screenshots / Output

One file, +3:

 ```bash
 webcmd hackernews top -f table
+webcmd hackernews top -f plain
 webcmd hackernews top -f json
 webcmd hackernews top -f yaml
 webcmd hackernews top -f md
 webcmd hackernews top -f csv
 ```

+`plain` prints `key: value` lines instead of a table, and prints the bare value when a command returns a single field named `response`, `content`, `markdown`, `text`, or `value`. It suits chat-style commands. `yml` and `markdown` are accepted aliases for `yaml` and `md`.
+
 Agents should use JSON unless they are presenting output to a human.
```

[github-actions]

🟢 No documentation gap found — medium confidence

The automated review found no documentation gap in the supplied changes.

This review is advisory and does not block merging.